1. Field of the Invention
The present invention relates to a jet printing ink composition. More particularly, it relates to a jet printing ink composition having firm adhesiveness on a surface of glass; ceramics such as earthen ware and porcelain; and plastics on which conventional jet printing ink compositions are not easily adhered; and also excellent water resistance, excellent ink droplet stability and uniformity and ink storage stability.
2. Description of the Prior Arts
Recently, various systems for jet print printer have been developed because the jet printing system is a non-impact system having excellent silent property at high speed without any adverse effect caused by a configuration of a printed surface.
For example, the ink jet process is classified to many ink misting type processes such as an Ink On Demand Type process which forms only desired ink droplets from a nozzle by a sudden volumetric change in an ink tank by a piezoelectric element resulting strain by electric pulse signal; an electrostatic attraction type process forming ink droplets from a top of a nozzle under a slight pressure applied to the ink and an electrostatic attractive force; a ultrasonic type process applying ultrasonic wave to an ink in a formation of an ink droplet from a top of a nozzle under an electrostatic attractive force; and a ink droplet type process for applying ultrasonic wave to an ink fed under a pressure.
The process for adhering an ink droplet formed from nozzles having a diameter of several micron meter to several millimeter can be classified as follows;
(1) a process for adhering ink droplets on a surface of a printed product after flying the droplets in a space; and
(2) a process for adhering ink droplets under an electric control such as an electric field control process for adhering ink droplets having electric charge on a desired position of a surface of a printed product by flying the ink droplets in an electric field and deviating the ink droplets by the electric field, a charge modulation process for adhering ink droplets having electric charge on a desired position of a surface of a printed product by charging a charge corresponding to a desired deflection by a pulse voltage to deflect the ink droplets in an electric field depending upon the charge of the ink droplets.
Various aqueous or oily ink compositions have been developed as the ink for the jet print printer. Most of the proposed ink compositions have inferior adhesiveness to glass and ceramics such as earthen ware and porcelain and have not satisfactory in a water resistance of a printed symbol or pattern, a dew inhibition and a solvent resistance.
It has been proposed for overcoming these disadvantages to use an ink composition comprising a novolac phenol resin and a small amount of a silane compound as a silane coupling agent as disclosed in U.S. Pat. No. 4,045,397. However, the ink composition comprising a silane coupling agent has not a satisfactory chemical stability, for example, the adhesiveness to glass etc. is remarkably deteriorated and a water resistance of the printed symbol etc. is remarkably deteriorated when the ink composition is used for the jet printing after a long storage.